The present invention relates to a sealed overmolded electrical cable and to a process for producing such a cable. More particularly, it relates to an electrical cable intended to be placed in a motor vehicle.
A motor vehicle is designed to encounter all kinds of traffic, climatic and load conditions, etc. As a result, all the equipment mounted on a vehicle must be capable of demonstrating defect-free operation whatever the traveling conditions of the vehicle. For this purpose, it is especially required that electrical apparatuses on board the vehicle be well sealed, not only with respect to water but also to fuels, engine fluids, etc.
Of course, this sealing is also necessary around the power supply for these various components, and therefore at the point of introduction of the power cable into an electrical component.
It is also necessary to guarantee that an overmolded power cable is sealed. This sealing is to be provided between the cable and the overmolding material.
Such overmolded cables are widely used, for example for wheel speed sensors, overmolded connectors on a cable, etc., but also in other environments which are less severe.
It is known to ensure this sealing by a superficial scratching of the cable sheath by grinding or milling. The cable thus prepared is then overmolded. However, such operations do not ensure sufficient sealing in the case of certain applications, for example for wheel speed sensors.
The object of the present invention is to obtain optimum sealing between the cable and the overmolded material.
For this purpose, the present invention relates to an overmolded electrical cable comprising, on the one hand:
a cable of the type composed of a plurality of insulated conducting wires inside an insulating sheath, and
an overmolding material encapsulating the insulating sheath over at least part of its length, said overmolded cable being characterized in that:
at least one groove is made in the external surface of the insulating sheath, said groove being suitable for accommodating the overmolding material.
Preferably, at least one fin forming an integral part of the sheath is made in the groove.
By virtue of such arrangements, the overmolded material cooperates not only with the groove made in the sheath, in order to ensure adhesive sealing, but also with the fin or fins in order to ensure cohesive sealing. For this purpose, the cooperation between the groove and the overmolded material enables these two materials to adhere perfectly to each other, even partially, over the entire range of their operating temperatures and whatever their respective expansion coefficients, whereas the cooperation between the fins and the overmolding material causes at least partial melting of the fins, thereby ensuring, after cooling, intimate cohesion between the two materials.
By virtue of this double (adhesive and cohesive) sealing, it is possible to guarantee optimum sealing of the overmolded cable according to the present invention.
Advantageously, in order to increase the degree of sealing, all that is required is to increase the number of grooves and/or the number of fins per groove.
It should also be noted that the profile of the fin has an influence on its ability to fuse with the overmolding material. Preferably, the thinner the fin the easier it is for it to melt. However, it is necessary to ensure that the amount of material coming from the fin remains in an amount sufficient to create homogeneous cohesion.
It should be noted that the grooves block the differential expansion that may occur between the material of the sheath and that of the overmolding. As regards the fins, these provide, by partial or indeed complete remelting, cohesion of the two materials.
It should also be noted that the sealing obtained according to the present invention is independent of the diameter of the cable and of the surface finish of the sheath. The sealing (by grooving) is also independent of the material pair chosen (cable and overmolding material) and of the design of the overmolding mold and of the processing parameters for the overmolding material.
Advantageously, the height of the fins made is less than the depth of the groove. Consequently, when the cable is handled before carrying out the overmolding operation, the fins are protected from any contact contamination (especially greases) which could cause deterioration of the cohesion between the fins and the overmolding material deposited subsequently.
The present invention also relates to a process for producing an overmolded cable. This process consists especially in:
making at least one groove in the insulating sheath and
overmolding the groove with an overmolding material in order to fill the groove and cause at least partial melting of the fin, so as to ensure sealing between the cable and the overmolding material.
Preferably, the process according to the invention also consists in creating at least one fin in the groove made.
Moreover, further objects, features and advantages of the present invention will become apparent from the description which follows, given by way of nonlimiting example and with reference to the appended drawings in which: